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prevent vtctld from creating tons of S3 connections #15296

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merged 5 commits into from
Mar 4, 2024
Merged

prevent vtctld from creating tons of S3 connections #15296

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dcdb7cf
prevent vtctld from creating tons of S3 connections
rvrangel Feb 20, 2024
f4976ed
add unit test
rvrangel Feb 20, 2024
d1a031e
goimports
rvrangel Feb 21, 2024
eff2a92
move function to struct
rvrangel Feb 29, 2024
13a3911
move to private contructor
rvrangel Mar 1, 2024
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20 changes: 17 additions & 3 deletions go/vt/mysqlctl/s3backupstorage/s3.go
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,9 @@ var (

// path component delimiter
delimiter = "/"

// use a shared transport for all connections
defaultS3Transport *http.Transport
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@mattlord mattlord Feb 28, 2024 •
edited
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Nit, but s3 is a bit redundant here. We can just call it defaultTransport.

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got rid of the global variable 😌

)

func registerFlags(fs *pflag.FlagSet) {
Expand Down Expand Up @@ -445,9 +448,7 @@ func (bs *S3BackupStorage) client() (*s3.S3, error) {
if bs._client == nil {
logLevel := getLogLevel()

tlsClientConf := &tls.Config{InsecureSkipVerify: tlsSkipVerifyCert}
httpTransport := &http.Transport{TLSClientConfig: tlsClientConf}
httpClient := &http.Client{Transport: httpTransport}
httpClient := &http.Client{Transport: getS3Transport()}

session, err := session.NewSession()
if err != nil {
Expand Down Expand Up @@ -496,6 +497,19 @@ func objName(parts ...string) *string {
return &res
}

// This creates a new transport based off http.DefaultTransport the first time and returns the same
// transport on subsequent calls so connections can be reused as part of the same transport.
func getS3Transport() *http.Transport {
if defaultS3Transport == nil {
tlsClientConf := &tls.Config{InsecureSkipVerify: tlsSkipVerifyCert}

defaultS3Transport = http.DefaultTransport.(*http.Transport).Clone()
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This seems correct after reading through: golang/go#26013

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I think that we should get rid of this getter and instead initialize the variable in init() though. This is a more clear signal of our intent and a more standard pattern. Does that make sense?

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yes, that makes sense. I will move it to the init() function. I will updated the PR tomorrow

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as mentioned in the other comment, I have moved this to the S3BackupStorage struct, so we don't need to initialise a global anymore 🙌

defaultS3Transport.TLSClientConfig = tlsClientConf
}

return defaultS3Transport
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Is this concurrency safe / does it need to be? Since it doesn't seem like it is.

I'm also not a big fan of having a global for this, those tend to bite us later on. Can we move it at least into S3BackupStorage instead then? That's still kinda global, but at least a tad better then.

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We can then also initialize it already in the init() to avoid the whole concurrency question / potential problem?

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yes, it should be, specially considering the default on the SDK already uses http.DefaultClient, which in turn uses http.DefaultTransport, this would have been a shared default in most projects that don't define their transport/client from scratch, see the Config docs.

I thought the S3BackupStorage would be created for each request being processed, but if that is not the case we could move it there. I will test it out and report back.

if the above is not possible and setting it up on init() is preferred I can do that too

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I see that you added a unit test for this. What's the conclusion?
@dbussink time for a re-review?

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@deepthi I’m back next week but I don’t see a refactor of this or a reason why that couldn’t be done. I strongly prefer not having a global like this if that can reasonably be avoided.

Also happy to push up that refactor once I’m back.

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I have moved this to inside the S3BackupStorage and re-run our tests and seems the connections are getting re-used, so I have update the PR to reflect that, thanks for pointing it out!

}

func init() {
backupstorage.BackupStorageMap["s3"] = &S3BackupStorage{params: backupstorage.NoParams()}

Expand Down
13 changes: 13 additions & 0 deletions go/vt/mysqlctl/s3backupstorage/s3_test.go
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Expand Up @@ -276,3 +276,16 @@ func TestSSECustomerFileBase64Key(t *testing.T) {
assert.Nil(t, sseData.customerKey, "customerKey expected to be nil")
assert.Nil(t, sseData.customerMd5, "customerMd5 expected to be nil")
}

func Test_getS3Transport(t *testing.T) {
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Nit, but TestGetS3Transport would be the typical name in the code base.

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I updated it to TestGetTransport to avoid the redundancy

transport := getS3Transport()

// checking some of the values are present in the returned transport and match the http.DefaultTransport.
assert.Equal(t, http.DefaultTransport.(*http.Transport).IdleConnTimeout, transport.IdleConnTimeout)
assert.Equal(t, http.DefaultTransport.(*http.Transport).MaxIdleConns, transport.MaxIdleConns)
assert.NotNil(t, transport.DialContext)
assert.NotNil(t, transport.Proxy)

newTransport := getS3Transport()
assert.Same(t, transport, newTransport) // new call should return the same transport
}
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